Vibrating conveyors have been used in the United States for over a century. Only within the past few decades, however, has there been extensive use of such conveyors. The successful application of various types of vibrating conveyors in different industries has resulted in an ever increasing demand for such conveyors.
Vibrating conveyors generally include a material-transporting trough driven by a controlled vibratory force which imparts a tossing, hopping, or sliding-type action to the material to be transported from one point to another. The vibratory force generator may be electromagnetic, electromechanical, pneumatic, or hydraulic.
One major factor that differentiates a vibratory conveyor from conventional materials handling equipment is that the material is "live" and moves independently of the conveying medium. In contrast, on a conventional belt conveyor, the material is static and only the conveying medium moves.
A variety of vibrating conveyors have been designed. Each design generally has similar basic elements: a trough in which the material is conveyed; a base which mounts the conveyor in place and ties all of the elements together; a trough supporting system to direct the motion of the trough; and a drive assembly such as an eccentric drive assembly which serves as a source of controlled vibrating motion applied to the trough. Many designs also include a reactor spring system which alternately stores and releases energy at each end of the trough stroke.
The trough is the only component that comes in contact with the material being conveyed. It may be fabricated from a variety of materials in almost any shape and size. The base is primarily a way of mounting the conveyor and usually incorporates structural steel members. It may be designed as an elaborate trusslike structure or may have a simpler design. The primary function of the trough supporting system is to control and direct the motion of the trough.
The drive assembly is the source of the controlled vibration. It may be in the form of a positive direct-connected linkage, a positive flexible-connected linkage, or a non-positive motorized counterweight assembly.
The reactor spring system may include steel coil springs, flexible steel or glass slats, rubber blocks, circular rubber toroids, or torsion bars. The particular application involved may make one type more advantageous than another.
A conventional vibratory conveyor is shown in FIGS. 1 and 2. Two major components of such a vibratory conveyor include the trough 2, and a drive assembly. In FIG. 2, the drive assembly includes actuators 4, 4'. The actuators 4, 4' are coupled to the side of trough 2 via a connecting rod 5. The rods 5 are typically welded to the side of the trough 2 and the actuator 4. The conveyor body is isolated from the floor or other supporting surface by damping isolators 6, such as springs or rubber shock absorbers. The actuators 4, 4' vibrate the trough 2 back and forth in the direction of the arrow 8, so that the vibration causes loose pieces of charge in the conveyor trough 2 to be thrown, and levitates them for a short time above the bottom of the trough 2. The actuators 4, 4' are connected to trough 2 at an acute angle a with the horizontal plane of the trough bottom. Within each vibration cycle, the pieces inside the conveyor receive an impulse up (a function of sin .alpha.) and forward (a function of cos .alpha.) and levitate. The trough is then moved down (a function of -sin .alpha.) and back (a function of -cos .alpha.). Therefore, when the levitated pieces fall back onto the trough 2 bottom, they actually move forward in the direction of arrow 10. This causes continuous movement of the loose charge in the trough from back to front, along the longitudinal axis of the trough 2 until the charge reaches the discharge end 14 of the conveyor.
A typical actuator 4 comprises ac motors and two eccentric weights 12a, 12b, mounted on opposite ends of the motor shaft. The conveyor includes two actuators 4 and 4', one on each lateral side of the trough 2. Each actuator is mounted at an acute angle a to the vertical. The motors provide rotation to the eccentric weights 12a, 12b, 12a' and 12b' of equal rotational speed .omega.. Weights 12a and 12b are mounted on their respective motor shaft to rotate in a direction opposite and 180.degree. out-of-phase relative to 12a' and 12b'. Forces produced by the rotating weights 12a, 12b, 12a' and 12b' substantially cancel each other along the transverse axis of the conveyor and add along the conveyor longitudinal axis. The force along the longitudinal axis is responsible for trough vibration and resulting movement of loose charge pieces.
When rotating weight actuators are used to provide the vibration force, an equal number of actuators are used on each side of the trough to eliminate transverse motion of the conveyor. Because these transverse forces are equal in magnitude and act in opposite directions, there is no net displacement of the conveyor trough in the transverse direction. However, in conventional conveyors these transverse forces generate severe destructive stresses in the individual members comprising the conveyor structure. To prevent damage from these forces to the conveyor members, the conveyor is constructed using heavy construction steel, adding to the size, weight, and price of the conveyor.
Even when a heavy steel construction is used, the connection point between the actuators 4, 4' and the trough 2 is continuously stressed due to the forces generated by the individual actuators. Eventually the weld connection between the trough 2 and the actuator 4 or 4' will fracture, potentially causing catastrophic results. Therefore, it is desired to have a vibratory conveyor assembly which better manages and withstands the destructive transverse forces, and which can be built less expensively, is more efficient, and more reliable.